Working Principle of Capacitance Continuous Level Transmitter?

• The probe forms a capacitance with the metalic tank-wall.
• The capacitance is sum of three capacitance:- C(air)=ε(air) x P x (H-L)
  C(material)=ε(material) x P x L
  C(residual) is due to device itself.
  
• Where ε(air) is the dielectric constant of air ≈1. ε(material) is dielectric constant of material. P is the constant of probe and installation, H is the active length of probe and L is the level of material
• Capacitance to level translation is performed with the aid of on-site calibration also called “wet-calibration”.

The device stores a low level capacitance as level for 4mA and high level capacitance as level for 20mA as defined by the user.